Estela de Carlotto isn't like most grandmothers. Instead of easing herself into retirement and enjoying the slower pace of life it affords, she remains a dogged workaholic.

Every weekday she rises early without fail in order to make the 70-mile round trip from her hometown of La Plata to an office in the Argentine capital, Buenos Aires.

"I had other ideas about what I'd be doing with my life, such as being with my children," she says, smiling. "I'm an elderly person who has had four children, and I now have 13 grandchildren and one great-grandchild. So I thought I'd be spending time with them. But life gave me another direction."

Since 1989 that direction has involved being a "professional" grandmother: As president of Abuelas de Plaza de Mayo (Grandmothers of Plaza de Mayo), she is the most visible face of one of South America's largest human rights organizations.

Nominated for the Nobel Peace Prize five times, the Abuelas group has members whose lives read like the pages of a horror novel. Born out of the atrocities committed during the country's last military dictatorship (1976-83) – which was backed by theUnited States – the group comprises mothers whose daughters and daughters-in-law were abducted and killed by the military regime for their leftist views.

But the armed forces had a perverse rationale. Women who were pregnant were kept alive until they gave birth. Their newly born children were then forcibly adopted by other families and given false identities: The military's aim was to ensure that they didn't grow up with the same political orientation as their murdered mothers.

The Abuelas are still searching for some 500 "stolen babies" – their grandchildren – who have grown up unaware of who they are (so far, 107 children, now adults, have been "returned" to their biological families thanks to DNA testing).

Of all the South American nations that lived through a dictatorship, Argentina is the only country that had a systematic plan involving the abduction of babies.

Ms. Carlotto's own daughter Laura was kidnapped in 1977 and killed in 1978 after she'd given birth to a son in captivity named Guido, after his grandfather. The body of Carlotto's daughter was returned to her by the armed forces, one of the few bodies returned to parents.

Despite more than 30 years of searching, Carlotto has never found her grandson. So what stops her from admitting defeat and making herself comfortable in her favorite armchair?

"Strength is love, you see," Carlotto answers. "They [the military] killed my daughter. I won't forget her, and I want truth and justice. I'm looking for a grandchild, too, which is also motivated by love, so there's no way I can stop doing what I'm doing."

The Abuelas president meets me at the group's central Buenos Aires headquarters. She enters the interview room with slow, considered steps. But when she sits down and fixes her gaze, her sharpness and determination are undeniable.

Carlotto, who used to be headmistress at a school, says she feels comfortable in her role and all that it entails, from having to deal with the emotional fallout of a nieto (grandchild) who has come to the Abuelas with doubts about his or her identity to meeting heads of states or being invited to functions by human rights groups around the world.

She also recognizes that what she does isn't for everyone. Other grandmothers have either found their grandchildren or want to take a back seat role. Or they simply don't have the energy that Carlotto continues to show. (Mariela Belski, executive director of Amnesty International Argentina, calls her a "tireless, committed, and persistent fighter for human rights, and the struggle's most emblematic voice.")